Depends upon how narrow you want the track. LOL. I'm not within 100 miles, but I know where 3 5x14 Haulmark trailers reside, and always for sale for the right price.
As for your concern, this is how torsion axle trailers behave when empty. There is not enough weight to flex the bushings, so they bounce down the road on any slight imperfection. As stated earlier, you can always lower the tire pressure when empty in order to provide some cushioning. I wouldn't go to 10 as the tow dolly puller, but dropping from 65 to 35 wouldn't hurt anything, just remember to fill them back to the max rating before loading.
